Self-adjusting stop means for the shoes of internal-expanding brakes



L. H. MOU LD June 10, 1947.

SELF-ADJUSTING STOP MEANS lFOR THE SHOES OF INTERNAL-EXPANDING BRAKES Filed March 19 1945 Patented June 10, 1947 i OFFICE 'SELF-YADJUSTING STOP MEANS FOR THE SHOES .OF INTERNAL-EXPAND- NG BRAKES Lyle Henry Mould, Lady Grey,fGape 1of 4Good Hope, Union of SouthAfrica 8 i Claims.

This invention relates `to self-adjusting stop =means 4for the shoes of :internal-expanding brakes, :and is fm'ore `particularly `applicable lto motor vehicle bra-kes 'of'the'lkindin which a pair of arcuate Aibralre Cshoes are .expanded against a brake Vdrum f-by hydraulic for mechanical `means operatingbetweentheir `two adjacent ends.

The :usual stop Vmeans employed `to limit the retracted position-of the shoes, consists of stop `bolts having cam-shaped 2heads, whichcamf bolts are providedat least one for eaohshoe, and are so arranged that each kbolt passes through Athe A'back-plate `of nthe Ibra/kev assembly lin lsuch a `position that the said cam-shaped lhead `'thereof bears edgew'ise against fthe inside of the shoe Ewhen lthe shoeis retractedito Aits Off position. Adjustment of fthis 'known device 'iseffected by 2loosening said fbolt, rotating lit 'the -required amount, `andftllereater'tighteningA it again. This 'manualvadjus'tment has to be effected periodically -asfthefbrake linings wear. An obiectof thepres- "ent invention is 'to -provide stop means vwhich -`are y*self-adjusting, iin fthat lthe :retracted position 'of albrake shoe is advanced automatically'asthe llinings :weargso Ithat the required clearance beitween the'brakeshoesrand the lbrake drum re- Q'mains-substantially constant,irrespectiveof wear of Ithe shoe 'linings `lI'l1eforego`ing and otherobjectsoi the invention are realized by the provision of a device which Jconsists of: aca-m pal-t 'which 'is rotatably Aassociated"with a locating part adapted to pro- "-ject through and 'be -Xed `to the vback plate of =theibrake assembly, so"thatsaidlcampart lis in a "position to co-act `cam fashion with the -back or @inside face of -a brake shoe; `spring fmeans tending to cause `rotation of the cam 4part `with -respect to the locating part in a direction tending to force the Ebrake shoe towards 'the brake drum; `and Yspring-urged frictional .retarding means interposed "between rthe edge of the "cam part land the brake shoe, the arrangement being Vsuch that the spring-urged fritional -retardn'g Vmeans land the spring means 'tending to `cause =ro`tation of the-cam part, are -so adjusted that the 'normal brake clearance is maintained 'and slipping "between the foam part and said frictional lretarizling'means to advance the retracted Vposi- 1vtiorro'f the shoe, takes place only as and `when ywearaoccurs 1in thebrake shoe lining.

it "is to be understood that the two spring ymean-s referred to .are so adjusted that, with the `.normal :application vofvthe brakes, and #the correct folearance, 'the .distance of travel `of a shoe from yits off for `retracted :position vto its` on f2 position, is `:insulcient Pto :reduce the :resilient pressure of the frictional -retarding means 'against Athe cam part, to permit -io Yrotational mOVementaOtsaid-camfpart. ,As Wear of the brake shoe lining takes place, however, Zthis .distance of `travel increases `until it :is suiicient `itc `.permit slipping of the cam part with `:respect #to ithe frictional fretarding means, fto take eplace, and thereby `to advance lthe :retracted position `of the shoe :and freduce ithe `clearance so as :to brlingtit back 'ftotthe normal amount. Means sareiprovzided forladjustinglthexspring 'lpressurecofzthe spring means itending to zcause rrotation :of 'the ecam part.

.Thetfrictional retardinglmeans is attached 'to the inner side face tof vabrake shoe, and, in zone dorm, is a flat leaiispr'ing.

11n :order .that the .inventionmayibe more kclearly .understood :and tcarried'vinto practice, 'referencefs inow :made zto :the accompanying drawings in `which like reference numerals :refer itc like aparts :throughoutthe severalviews.

In fthe drawings Fig. 1 is a sectional sideeleVationfnf-oneihalf 1of a .brake assembly to which Vthe invention is shown applied;

Fig. `2 'is a A-fragmentary sectional plan `View Ataken through `the fbrake :assembly shown in tig` l, and illustrating a preferred fformfof the invention.

Fig 3 is lasecti'onal View of'an alternative rform of y device constructed according ato `the invention Vand Kadapted for .use 'in cases where .insuicient "space texists inside the back-plate vto accommofdate all theoperative iparts of the=device:

Fig. 4 is a -view similar to -Fig.i2ishowing another modification `of the Ainvention similar to thatShOWninFigBg Fig. `5 `is aesectional View `of the `deviceshown Fig. `6 `is .a sectional View Aof `the Vdevice .shown IinAEig. 4, `but with the addition .of `a dust soap;

@Eig .7 'is a .perspective fexploded View Ldi `the "device of Figs. .-2 and -5, shown to -a larger scale;

Fig. -8 fis a "similar view .of the `.device -of `Eigs. `4 and-but'excluding the dust cap and liig. 49 `is .ia perspective View vof ythe ffrictional fretarding leaf-spring. v

Referring toitheidrawings generally, reference numeral I denotes afbrake `drum while reference lnumerallshows an Varcuate brakefshoe provided with `arbrake lining 3, arranged to Vceo-act therewith `in :known manner, such as yby -means of `the 4hydraulic cylinder `#i :secured to :the `usual back -plate;5.

Referring to Figs. i2, f5 and "7, the device lfoonsists of a cam part provided with an integrally formed sleeve-like boss 1, by means of which it is rotatably mounted on the inner end of the locating part in the form of a pin 8 provided with an intermediate collar portion 8 and having its outer end screw-threaded to receive the securing nut I8 by means of which the device as a whole is fixed to the back plate 5. The cam part is secured on the pin 8 by the spring clip II which engages in a groove I2 provided on the inner end of said pin 8. Threaded over the sleeve-like boss 1 is the coiled spring I3, which has one end anchored to the cam part 6 by being bent to hook form and inserted through a hole I4 therein. The opposite end,

Y likewise bent to hook form, is anchored by engaging with the anchor peg I5, inserted in the pin 8 on the inner side of the collar -8 thereof. The projection I6 on the end of the boss 1 coacts with the anchor peg I5 for purposes of retaining a minimum torsional loading of the spring I3. A loose guard ring 48 which is arranged to nt over collar 8, is a sliding t on the boss 1, and is provided for the purpose of preventing the end coils of the spring I3 from entering the space between the end of the boss 1 and the collar 9 and thereby tending to interfere with the proper functioning of the device. The ring 46 is slotted at I1 to provide clearance for the anchor peg I5. As shown in Figs. 1 and 2, the edge of the cam part 6 is arranged to be in constant contact with the frictional retarding leaf spring I8 which is immovably secured by its end I8 (see Fig. 9) to the inside face of the brake shoe 2 by the rivet or screw 28. The opposite end, provided with hole 2|, is located by the stop screw or rivei-l 22 in such a manner as to permit free flexing movement within limits. The leaf spring I8 is bent outwardly as shown at 23 to provide stop means limiting the rotational movement of the cam part 6 after it has reached its maximum adjusted position. The device operates as follows:

The brake shoes 2 are normally held in the olf position against the rotatable cam parts 6,

Fig. 1, by the brake shoe return springs in which position the leaf springs I8 are compressed between the cam part 6 and brake shoes 2.

When the brake is applied, the free ends of the brake Shoes, adjacent to the brake cylinder 4 are forced outwardly and away from the cam parts 8 toward the brake drums. The tension of a leaf spring I8 allows its free or movable end portion to keep in contact with its cam part 6 thereby preventing the cam from rotating.

When the brake is released, the shoes return to the off position, compressing the springs I8 between them and the cam parts. The movement of the spring I8 is limited by the shouldered stop rivet 22. As the brake linings wear, the brake shoes 2 must move farther away from the cam part 6 when the brakes are applied, until rivet 22 acts as a stop for the lmovable end of the spring I8 and carries it with the shoes away from its cam part 8. Its pressure against the cam part 6 is, therefore, released Which allows the cam part to be rotated by the spring I3 (Fig. 7), 'bringing a wider portion of the cam part into contact with the spring I8.

When the brakes are now released, the shoes again compress springs I8 as they return to the new off position, which will be in advance of the previous 01T position by the extra width introduced by the cam during its rotation, for

example if the extra width of cam introduced 4 between its spindle 8 (Fig. 7) and the brake shoes, is 1A; inch then the shoes will be 1/8 inch nearer thebrake drums when they are in the off position, than they were before the cam rotated.

The movement` of the brake shoes is limited by and corresponds to the free movement of the spring I8, its free movement being limited by the stop rivet 22 (Fig. 1) to the preset minimum necessary for free operation of the drums when the brake is off.

If for example, the normal movement of the brake shoes, from the off to the full on position is 1/8 inch and the brake linings wear 1% inch the rotatable cam will, when the brake is fully applied, revolve enough to remain in contact with the spring I8 as the spring is carried away with the shoes and thereby introduce a portion of the cam that is le inch wider than that which was in contact with the spring before the brake was applied.

Fig. 3 shows an alternative form which the device may take for use in brake assemblies in which there is insufficient space on the inside of the back plate 5a to accommodate all the operative parts of the device. In this case the cam part 6, which is the only moving part located on the inside of the back plate 5a, is provided with a spindle 24 which is rotatably assembled in the bore of the locating part 25 which is in the form of a sleeve having a flange 2B at one end and with that portion of the sleeve 25 adjacent the ange 26, screw-threaded to receive the securing nut 21. The coiled spring 28 (corresponding to the spring I3) is in this case threaded onto the outer end portion of the sleeve 25 and has one end anchored to the back plate 5a by being bent so as to project through a hole 29 therein; while the opposite end is anchored to the protruding end of the spindle 24 by means of an anchor pin 38 and collar 3l. The anchor pin 38 passes through the collar 3l and the protruding end of the spindle 24, and thereby keys said collar thereto. A projection 32 on the collar 3| co-acts with a corresponding projection on the outer end of the sleeve 25 to provide stop means for torsionally loading the spring 28. The projection to the end of the sleeve 25,4 (not shown) is similar to the projection I8 on the sleeve 1.

Figs. 4, 6 and 8 show a preferred modification of the alternative form of the device shown in Fig. 3. In-this case a sleeve 33, corresponding to the sleeve 25 of Fig. 3, but made shorter, is screw-threaded for the whole of its length beyond the collar 28a, with which screw-threaded portion a flanged securing nut 34 co-acts for xing the sleeve 33 to the back plate 5a. In addition a collar part 44 corresponding to the collar 3l of Fig. 3, is provided with a sleeve-like extension 35, having a projection 36 on its end adapted to co-act with a projection 31 on the end of the sleeve 33 to provide stop means for torsionally loading the spring 38, (corresponding to the spring 28 of Fig. 3), which is threaded onto the said sleeve-like extension 35 over the guard sleeve 39 which is provided to prevent the end coils of the spring 38 from slipping into the space between the ends of the sleeve parts 33 and 35 and thereby tending to interfere with the propervoperation of the device. The collar part 44 is keyed to the spindle 24 by the split pin 48 which also provides anchoring means for the outer hooked end of the spring 38, the opposite hooked end being anchored to the flange Voffthe nut `Sil Lby engagingyiinaslot 4H therein. To Aprotect 4the moving :parts against dust fand wind, a dust nap ".4f3.izis.;arranged"to 'be screwed onto the "flange ofthe'nut 34 as shown in Fig. 6.

What I claimis:

1. Self-adjusting stop means for a shoe of an A internal-expanding brake lassembly of .the Acharacter described and including `a brake drum and a back platesa-idstopmeans comprising a locating partprojecting through and fixed to the said back Lplate, a cam part rotatably associatedwith said locating part, `the -parts v"being so positioned relative to the brake shoe that said cam part coacts in cam fashion with an adjacent portion of the brake shoe, spring means tending to cause rotation of the cam part with respect to the locating part in a direction tending to force the brake shoe towards the brake drum, and springurged frictional retarding means interposed between the edge of the cam part and the brake shoe', the spring-urged frictional retarding means and the spring means tending to cause rotation of the cam part, being so adjusted that the normal brake clearance is maintained and slipping between the cam part and said frictional retarding means to advance the retracted position of the shoe, takes place only as and when wear occurs in the brake shoe lining, and means for adjusting the spring pressure of the spring means tending to cause rotation of the cam part.

2. Self-adjusting stop means for a shoe of an internal-expanding brake assembly of the character described and including a brake drum and a back plate, said stop means comprising a locating part projecting through and xed to the said back plate, a cam part rotatably associated with said locating part, the Darts being so positioned relative to the brake shoe that said cam part coacts in cam fashion with an adjacent portion of the brake shoe, spring means tending to cause rotation of the cam part with respect to the locating part in a direction tending to force the brake shoe towards the brake drum,

and spring-urged frictional retarding means interposed between the edge of the cam part and the brake shoe, the spring-urged frictional retarding means and the spring means tending to cause rotation of the cam part, being so adjusted that the normal brake clearance is maintained and slipping between the cam part and said frictional retarding means to advance the retracted position of the shoe, takes place only as and when wear occurs in the brake shoe lining, and means for adjusting the spring pressure of the spring means tending to cause rotation of the cam part, the said frictional retarding means being a flat leaf spring iXed to the inside face of the brake shoe by its ends, the intermediate portion of said spring beine spaced from said face to provide clearancefor flexing movement, means xedly securing one end of said spring, so that while its outward exing movement away from the shoe is limited, it is free to move inwardly, as when it makes contact with the cam part on retraction of the brake shoe.

3. Self-adjusting stop means as dened in claim 1, said cam part being provided with a boss of sleeve form and said locating part being in the form of a collared locating-pin having its outer end screw-threaded and having said boss of sleeve form rotatably mounted on its inner end, a nut on said screw-threaded end whereby the locating-pin may be attached to said back plate, and the spring means tending to cause rotation of the cam part, consisting of a coiled @,421 ,eea

.f6 spring threaded onto the said boss A'thereof fand having one -end anchored thereto, land means anehoringthe oppositeendof said coil spring to theaforementioned collaredpin `"in Self-adjusting stop -means `as .defined claim 1,saidcampart1being provided with -a i, boss of `sleeve Aform mand :said 4locating part `being lin the for-m lof a V'oo'llared locatingpin "having fits nouter -end screw-threaded Land fhavinfg said `boss of sleeve form'irotatably-mountedpnits'inner end, a -nut on said screw-threaded end `whereby Ithe rlocating-#pin may be attached to said :back plate, and the spring means tending to cause rotation of the cam part, consisting of a coiled spring threaded onto the said boss thereof and having one end anchored thereto, and an anchor peg on said collared pin for anchoring the opposite end of said coil spring.

5. Self-adjusting stop means as deiined in claim 1, said cam part being provided with a boss of sleeve form and said locating part being in the form of a collared locating-pin having its outer end screw-threaded and having said boss of sleeve form rotatably mounted on its inner end, a nut on said screw-threaded end whereby the locatingpin may be attached to said back plate, and the spring means tending to cause rotation of the cam part, consisting of a coiled spring threaded onto the said -boss thereof and having one end anchored thereto, an anchor peg on said co-llared pin for anchoring the opposite end of said coil spring, and a projection on the end of said boss co-acting with said anchor peg to act as stop means for the purpose 0f retaining a minimum torsional loading of the coil spring.

6. Self-adjusting stop means as defined in claim 1, said cam part being provided. with a spindle and said locating part being in the form of a sleeve having one end flanged, a portion of the sleeve adjacent said flanged end being screwthreaded, said spindle being rotatably assembled in the bore or said sleeve with one end of the spindle protruding therefrom, a nut on said screw-threaded end whereby the locating part may be secured to said back plate, or coiled spring threaded over the outer end of said sleeve and having one end thereof anchored to the back plate and the opposite end to the protruding end of the spindle of the cam part.

7. Self-adjusting stop means a-s defined in claim 1, said cam part being provided with a spindle and said locating part being in the form of a sleeve having one end anged, a portion of the sleeve adjacent said flanged end being screwthreaded, said spindle being rotatably assembled in the bore of said sleeve with one end of the spindle protruding therefrom, a nut on said screw-threaded end whereby the locating part may be secured to said back plate, or coiled spring threaded over the outer end ofsaid sleeve and having one end thereof anchored t0 the back plate and the opposite end to the protruding end of the spindle of the cam part by means of a collar and anchor pin, said pin keying said collar to said cam spindle, said collar being provided with a projection, the outer end of said locating sleeve being provided with a corresponding projection,

and said projections co-acting to provide stop means for torsionally loading said coiled spring.

8. Self-adjusting stop means as defined in claim l, said cam part being provided with a spindle and said locating part being in the form of a sleeve having one end flanged, said sleeve being screw-threaded over the entire length thereof, said spindle being rotatably assembled in the boreof the sleeve with one end of the Vspindle protruding therefrom, a anged securing and means keying said collar member to the end of said spindle, the other end of said coiled spring being anchored to said keying means. -Y

LYLE HENRY MOULD.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Name Date Cowell June 6, 1944 Number 

